In the late 1770s members of high society travelling through Devizes on their way to Bath would often stop off at the town's public houses for a night of repose. The Bear Inn was a particularly popular spot, thanks to the astonishing talents of the landlord's son who, at the age of five, entertained guests by crafting near-perfect pastel renditions of his sitters for a guinea.

The young boy's name was Thomas Lawrence, a child prodigy who went on to become one of the most successful painters of the Regency period.

Now a new exhibition of his work – the first in Britain for more than 30 years – hopes to resurrect Lawrence's reputation as one of Britain's most formidable and talented portraitists.

The exhibition will open at the National Portrait Gallery in October and go on tour in the US next year. For connoisseurs of Regency art it is a remarkable event because much of Lawrence's work is rarely seen in public.

Among the 54 paintings on display will be a trio of works which are usually only visible at Windsor Castle's Waterloo Chamber. The chamber, built to celebrate the defeat of Napoleon, features some of Lawrence's grandest paintings, including portraits of Charles, the Archduke of Austria, and Gebhardt von Blücher – the Prussian general whose arrival at the Battle of Waterloo helped turn the tide against France. The two previously unseen portraits, meanwhile, are of the Countess Thérèse Czernin and Lady Cahir.

Peter Funnell, the National Portrait Gallery's curator of 19th-century art, said he hoped that the exhibition would help Britons rediscover a painter who was lauded when he lived but was quickly forgotten after his death in 1830.

"Lawrence's reputation diminished very rapidly when he died because of the Victorian evangelical backlash to the Regency period," he said. "But he really was one of the period's finest painters. He is a strikingly innovative painter who created works that are beautifully rendered and a joy to look at."

Lawrence's father was very proud of his son and would often greet guests at his inn with the words: "A recitation or your portrait, sir?" But it seems he was less talented at business than his son who, as a young teenager, became the major breadwinner for the family.

By 1782 the Lawrence family had settled in Bath and largely relied on Lawrence's portraits to provide their income. Within five years the young painter's reputation had blossomed to such an extent that he was taken under the wing of Sir Joshua Reynolds as soon as he arrived in London.

Alongside his bitter rival Thomas Gainsborough, Reynolds pioneered the Grand Style – a form of painting that attempted to recreate the grandeur and skill of the high Renaissance. His friends and fellow artists helped to found the Royal Academy and they regarded history painting as the highest form of art.

But it was primarily the portraiture of Britain's growing aristocracy that kept the money rolling in, and it was into this world that Lawrence was swiftly adopted upon his arrival in London. By 1791, at the age of 22, he had already been accepted into the Academy. The death of Reynolds a year later opened royal doors for his protégé, who was appointed the main painter to King George III and, later, his son, George IV, who ruled as Prince Regent during his father's madness.

Lawrence's paintings of the Prince Regent are some of his most famous, numerous – and flattering – works. He was renowned as a notoriously obese lecher, but Lawrence, in the manner of all good portrait painters of his time, depicted his subject as a slim, majestic leader, draped in finery and medals.